This application is in the field of mass spectrometers and, more specifically, relates to a mass analyzing spectrometer and a method for fabricating curved, heated ion transfer optics. Various mass spectrometers are known in the art. An example of a prior art multi-pole mass spectrometer is illustrated in FIG. 1. For convenience of description, the mass spectrometer example of FIG. 1 is specific to a quadrupole mass analyzer; however embodiments of the invention may be used in other types of mass analyzers. In the mass spectrometer of FIG. 1, the sample molecules are delivered, e.g., by injector 105, into an ionization chamber 110, which ionizes the molecules, thereby acting as an ion source 110. Ions from the ion source 110 are focused and transferred to the mass analyzer 125 via ion guide or transfer optics 115, which is driven by voltage generator 120.
As shown in FIG. 1, four conductive rods, constituting the quadrupole mass analyzer 125, are arranged in two pairs, each pair receiving the same DC+RF signal, denoted as U+V cos(wt), wherein U is the magnitude of the DC voltage while V is the magnitude of the RF signal. One pair of rods receives a positive DC signal at zero phase, while the other receives a negative DC signal at 180 degrees phase (−[U+V cos(wt)]), thereby acting as a band pass separating the ions according to their mass to charge ratio, generally denoted as m/z. This relationship is illustrated in FIG. 2, wherein the shaded area denotes the band-pass wherein only ions having a mass to charge ratio (m/z) within the shaded area may pass the mass analyzer. The width of the band pass is controlled by the signal applied to the rods, such that the narrower the band pass is, the higher the resolution of the mass spectrometer.
By scanning the magnitude of U and V, one can, over time, allow species of different mass to charge ratio to pass through the spectrometer, thereby obtaining a spectrum of the ion species within the sample material. Generally, during the scanning process, the ratio UN is kept constant so as to maintain the same band pass. The ions exiting the mass analyzer 125 are detected by detector 145. As shown, controller 140 controls the power applied to the focusing optics and the mass analyzer 125.
Transfer optics are incorporated in various designs of mass spectrometers, such as the instrument described above. The function of the transfer optics is to transfer the ions generated in the ion source into the mass analyzer. The transfer optics can be used to extract the ions from the ion source and focus the ions into a beam that is then transferred into the mass analyzer. The transfer optics can also be used to bridge the pressure difference between the pressure inside the ion source 110 and the pressure inside the mass analyzer 125.
As ions exit the ion source and enter the transport optics, some ions may be deposited on the electrodes at the inlet of the assembly. If an insulating deposit is formed, a surface charge may result, which would lead to modified electric fields and degraded performance. The charge build-up leads to modified electrical field within the transport assembly, thereby degrading its performance.
Accordingly, there is still a need for an improved and effective transfer optics.